This invention relates to control and diagnosis of driver circuits and wiring harnesses for electrical load devices, including electromagnetic actuators and resistive devices such as lamps.
Electric load devices such as electromechanical actuators and lamps are used in a variety of applications in industrial controls, motor vehicles and other devices. Industrial applications include, for example, robotics and electrically controlled valves for chemical process systems. Vehicle applications may include fuel injection systems, electronic transmissions, evaporative purge control systems, antilock braking systems, intake/exhaust valve control systems, lighting systems and others. Typically a circuit will comprise the load device located in a remote area where control or power is needed with a remote driver that is connected to the driver with a wiring harness.
A circuit for an electric load device is used primarily to control the device, but may also be used to monitor performance of the device. When a fault occurs in a circuit, the effect in an industrial setting will be machine downtime and a resulting loss in productivity. The effect on a motor vehicle can include unacceptable system performance and damage to related systems and components, or an increase in emissions of the vehicle. The increase in emissions has become important with the advent of government regulations that compel addition of on-board vehicle diagnostic systems to monitor emissions related components and control systems. The intent of the on-board diagnostic systems is to detect faults that lead to emissions increases.
There is a need to identify a specific location of a fault once it has been detected to ensure that any fault can be quickly located and effectively repaired. This need to identify the location of a fault is important to minimize a loss of productivity associated with machine downtime in a factory, or to minimize costs to diagnose and repair a system on a vehicle.
When a fault occurs in a system, there is a need to identify the type and location of the fault to facilitate repair. When a fault occurs on a vehicle a diagnostic fault indicator may be set. This fault indicator typically will identify the system where a fault has occurred, but will lack sufficient specificity to identify where a specific repair needs to occur. The diagnostic fault indicator will lead a repair technician to a system whose performance may be affected by an interaction of several components or subsystems. The technician may be compelled to work through multiple diagnostic procedures to locate and repair the fault. This consumes time and resources, and results in increased cost and decreased satisfaction to the vehicle owner.
The ability to correctly detect and identify a fault is more difficult when the fault is intermittent, as may occur when there is water intrusion into a wiring harness or connector. A technician will spend time and resources in attempting to reproduce failure conditions to identify a fault or verify a repair. This can result in customer dissatisfaction and high costs to the customer or the manufacturer, due to multiple attempts to identify and repair intermittent faults in a circuit. This problem is apparent when a fault occurs that sets a general diagnostic code that lacks sufficient specificity to identify a needed repair.
Electric load circuits can include devices such as insulated wires, connectors, drive transistors or relays, wiring junctions, and fuses. Faults in the circuit that can lead to undesirable operation of an electric load system include wiring harness shorts to ground, wiring harness open circuits, and wiring harness intermittent connections. Other faults include broken or abraded wires, and connector faults such as relaxation of terminals, or corrosion due to intrusion of water or contaminants.
There are standard methods existing to diagnose and repair faults using off-board techniques such as connectivity tests and diagnostic trouble trees. These methods and tools are contained in service manuals, and are well known in the art. Off-board techniques require the employment of intrusive test methods, including the use of hand held scan tools used by a skilled technician. The prior art has sought to diagnose faults in electrical load circuits on-board the vehicle through the addition of current-monitoring devices that add cost and complexity to the circuit. These may be effective in diagnosing fault in a specific solenoid, but do not diagnose faults in the circuit leading to the electrical device. The prior art has also sought to identify the presence and location of faults with on-board intrusive methods and systems that send a signal through a circuit to a device and look for an subsequent output from the device. These methods can be disruptive when they occur during normal operation of the vehicle or the system. The prior art also has not addressed the issue of identifying the presence of an intermittent fault in a circuit, and the related result of being able to focus the repair efforts of a technician to a specific location in the system.
The present invention is an improvement over conventional electric circuit monitoring devices in that it provides a device and method to passively monitor the performance of an electrical circuit to a load device, including faults that occur intermittently. The invention is capable of identifying the location and type of malfunction in the event of a fault. Accordingly, the invention provides a complete apparatus and method to control and diagnose driver circuits for electromagnetic actuators and resistive load devices, and detect faults therein.
The present invention includes a circuit and methods that are able to control and monitor an electric load. It includes the electric load, a first switch electrically coupled to a power supply and one end of the electric load, and a second switch electrically coupled between the second end of the electric load and ground. The switches are controlled by a load drive controller that communicates with an external controller. Detection of a fault condition in the circuit occurs by comparing an electric potential at one end of the electric load with a first known potential, and by comparing an electric potential at the second end of the electric load with a second known potential. The circuit accomplishes the comparison using, for example, discrete electronic comparators. The inputs from the electric load and the first and second known potentials are appropriately biased with an effective amount of electric potential to enable detection of a type and location of a fault condition. The output from each of the comparators is communicated as an indication of a fault. This is a passive monitoring system. When a fault is detected, the circuit will operate to identify a location and type of fault, by controlling the switches and monitoring the output of the comparators. The output from the comparators can be communicated to an external controller to indicate the type and location of the fault.
The present invention also comprises a method for controlling and monitoring an electric load. This includes providing a circuit comprising an electric load with a first switch electrically coupled between a power supply and the electric load. The circuit also includes a second switch electrically coupled between the electric load and ground, and a load drive controller operable to control each switch. The method operates by activating the switches. It then compares an electric potential at the first end of the electric load with a first known potential, and also compares an electric potential at the second end of the electric load with a second known potential. The method will then obtain an output from each comparison. The output can then be communicated to an external controller to indicate a fault. The method can also detect the type and location of any fault condition using the comparison of electric potentials. The electric potentials at the first and second ends of the electric load and the first and second known potentials are appropriately biased to detect the type and location of a fault condition. The outputs from the comparisons are then communicated and indicate the type and location of the fault.
A feature of this invention is to provide a circuit to control an electric load and monitor for faults in the circuit. The circuit is also able to identify the type and location of a fault, and communicate this information.
Another feature of this invention is to provide a method for controlling an electric load and monitoring for faults in the circuit. The method is also capable of identifying the type and location of a fault, and communicating this information.
These and other features of the invention will become apparent to those skilled in the art upon reading and understanding the following detailed description of the embodiments.